<template>
	<ul class="list">
		<li class="item" 
			v-for="item of letters" 
			:ref="item"
			:key="item"
			@touchstart.prevent="handleTouchStart"
			@touchmove="handleTouchMove"
			@touchend="handleTouchEnd"
			@click="handleLetterClick"
		>
			{{item}}
		</li>
		
	</ul>
</template>

<script>
	export default {
	  name: 'CityAlphabet',
	  props:{
	  	cities:Object
	  },
	  computed: {
	  	letters () {
	  		const letters = []
	  		for (let i in this.cities) {
	  			letters.push(i)
	  		}
	  		return letters
	  	}
	  },
	  data () {
	  	return {
	  		touchStatus:false,
	  		startY:0,
	  		timer:null
	  	}
	  },
	  updated () {
	  	this.startY=this.$refs['A'][0].offsetTop
	  },
	  methods:{
	  	handleLetterClick (e) {
	  		//向外触发一个事件
	  		this.$emit('change',e.target.innerText)
//	  		console.log(e.target.innerText)
	  	},
	  	handleTouchStart () {
	  		this.touchStatus=true
	  	},
	  	handleTouchMove (e) {
	  		if(this.touchStatus) {
	  			if (this.timer) {
	  				clearTimeout(this.timer)
	  			}
	  			this.timer = setTimeout(() => {
	  				const touchY =e.touches[0].clientY - 79
		  			const index = Math.floor((touchY - this.startY) / 20)
		  			if (index >= 0 && index <this.letters.length){
		  				this.$emit('change',this.letters[index])
		  			}
	  			},16)
//	  			console.log(index)
//	  			console.log(touchY)
	  		}
	  	},
	  	handleTouchEnd () {
	  		this.touchStatus=false
	  	}
	  }
	}
</script>

<style lang="stylus" scoped>
	@import '~styles/varibles.styl'
	.list
		display:flex
		flex-direction:column
		justify-content:center
		position:absolute
		top:1.54rem
		right:0
		color:$bgColor
		/*background:red*/
		bottom:0
		width:.4rem
			.item
				line-height:.4rem
				/*padding:.06rem 0*/
		 		text-align:center
</style>